Biological Imperative
by Sunsetter Nymphetamine
Summary: Alpha, Beta, Omega. From childhood they learn their goals and their purpose. It is all about the biological imperative. Dean Winchester is not sure what exactly drives him to help the strange, abused Omega who shows up on his doorstep in the dead of night, but as he grows closer to the man, he cannot help but wonder if there is more to love than simple biology.
1. Chapter 1

A/N: Hey all! So, this is my foray into that weird world known as Omegaverse. I was always a bit troubled by the lack of Omega/Omega or Alpha/Alpha stories out there, so I decided to write one myself. This is the result.

* * *

"Hey there gorgeous, come here often?"

Dean scowled, the heavy, musky sent of Alpha assaulting his nose as a large, balding man leaned over him, crowding into his personal space. "Go away," he snapped, downing a gulp of Sam Adams. Typical. Go out to a bar to drink away a long day at work, and get hit on by a creepy sleazebag. It was almost pathetic, how he had come to expect this turn of events.

"Just trying to be friendly, babe." Dean growled low in his throat as the Alpha laid a large, meaty hand on his shoulder. "What's a pretty little thing like you doing here alone and unmated? You don't smell like you've got an Alpha or Beta around to take care of you."

"Don't want one, don't need one." Dean twitched, shrugging out of the stranger's gasp. "I told you to go away."

"There's no need to play hard to get." The man plunked himself down in the chair next to Dean, offering him a large, cheesy grin. "The name's Zachariah. Why don't you tell me your name?"

"Yeah, sure. It's 'the Omega who's going to get you thrown out of this bar if you don't fuck off,'" Dean snarled, glaring at the interloper. "I'm here for a drink, not a hook-up. Try someone else."

"Well, what crawled up your ass?" Zachariah asked, peeved, scowling at Dean.

"Not your dick." With a sigh, Dean tossed back the rest of his beer and set the bottle down on the counter. "Hey Ellen, I'm out!" he called, catching the no-nonsense woman's eye and flashing her a charming grin.

"And what do you want me to do about it, Winchester?" she called good-naturedly, flicking her fingers in his general direction. She laughed as Dean pouted dramatically, the smile in his eyes belying his expression. "Yeah, yeah, hold your horses, kiddo. Let me finish getting this shot tray together."

Dean grinned, leaning back easily in his chair. He was acutely aware of Zachariah's presence next to him, but he'd smelled threatening Alphas before, and while the man was annoying and presumptuous, he was not a creep—not really. Dean could tolerate annoying as long as it didn't delve into predatory. He would really hate to break out the pepper spray tonight.

Dean knew that as an attractive, single Omega at nearly thirty, he was an oddity in their society. Practically from birth, he, like everyone else he knew, had had the social order drilled into his head. Life was all about the biological imperative; everyone was supposed to spend their first few decades seeking out a mate, maybe even a few, and eventually settle down and raise a family. Alphas were biologically geared towards taking care of Omegas and Betas, Omegas naturally gravitated to the protection of Alphas and Betas, and those damn lucky Betas could settle down with whoever the hell they wanted to, even members of their own sex. The entire point of forming bonds was passing on genes, and the human race had evolved in such a way as to attract the best mate for that purpose.

Dean supposed that he was simply a genetic freak. The heavy musk of an Alpha held no erotic pull for him, and the crisp, clean scent of a beta left him neutral and cold. He could never seem to find an Alpha or a Beta with whom he wanted any more than friendship, or perhaps brotherly camaraderie. No, nothing set fire to his veins like the sweet, sugary scent of a fellow Omega, so soft and tantalizing that it made him ache with longing. Never in his life had Dean heard of such an anomaly as himself. Were it not for his own scent, rich and heavy with undertones of honey and sugar, were it not for the heats that plagued him every month or so, for the slick that dribbled down his thighs whenever he was particularly aroused, he would have thought that perhaps he was just a particularly unusual Beta. But biology didn't lie, at least not to such a degree, and Dean had simply resigned himself to a life of celibacy and spinsterhood.

Sometimes, Dean wondered what it would be like to be normal. To cry for the knot of an Alpha or the hands of a Beta during the agony of his heats, rather than sobbing for the gentle caress of one of his own kind; to settle down with a mate and raise a family. His younger brother, Sam, seemed to have no such genetic defect. Sam was every inch the perfect Alpha, strong and domineering, doting upon Kevin, his Omega spouse, just like a fairy-tale lover. His parents, too, fit the mold, Alpha husband and Beta wife, every inch the perfect family. The thought had plagued him in his younger years, but the angst of his situation had long since worn off. As far as things went, Dean was content, happy to enjoy the single life, focusing on family, friends, and career.

Several beers later, Dean left the bar, only slightly drunk and most likely below the legal blood-alcohol limit. With a contented sigh, he slid into his car, a gorgeous 1967 Chevy Impala and his most precious possession. Really, with a fast car, a strong set of friends, wonderful parents, and an amazing brother, what more could he need? Certainly not a mate. Dean Winchester might be an Omega, but he was his own person. He did not need an Alpha or a Beta to order his life, dominating him in bed and possibly outside of it. As for children, well, Sam was perfectly capable of carrying on the family line. Dean grinned, ACDC blasting from the Impala's speakers as he sped home, more than ready for a night alone and unbothered in his bed, able to wake up rested and fulfilled for work in the morning.

0o0o0o0o0

Castiel MacLeod could not help but flinch at the sound of a key scraping in the lock to the front door. "Listen to me, Samandriel," he murmured, pressing a shaky kiss to his six year old son's forehead. "Daddy wasn't in a good mood when he left for work. I want you to be on your best behavior when he comes in, okay? Can you do that for me?"

Samandriel nodded, his wide blue eyes huge in his thin, pale face. "Yes, Papa," he said seriously, reaching for Castiel's hand. Castiel offered his child a shaky smile and sank to his knees, ostensibly to better help his son with the large puzzle spread out on the living room floor, but in the back of his head, he knew that it was a gesture intended to soothe his mate. Fergus Crowley MacLeod, best known as Crowley to his friends and family, had a short temper and expected submission in every way from his spouse, especially after a long day at work. Castiel kept his head bowed as footsteps sounded in the hall, his hand shaking slightly as he helped Samandriel fit a particularly stubborn piece into the border of the puzzle.

Samandriel stiffened beside Castiel, and Cas knew that his mate had entered the room. "Hello, Dear," he said softly, glancing up without meeting Crowley's eyes. He would rather not spark his husband's ire by breaking his rules so early in the night.

"Hello, Castiel, Samandriel," Crowley replied, his accented voice crisp and loud in comparison to Castiel's. "Working on a puzzle, I see?"

"Yes," Castiel replied softly, dusting off his hands and rising carefully, keeping his head bowed in submission. "We've gotten pretty far in it over the past few hours."

"Didn't put you off making dinner, I hope?" Crowley asked, an edge to his voice that Castiel picked up only after long years of practice.

"Of course not," Castiel replied quickly, smoothing his hands over his rumpled button-down. "There's a roast in the oven. It should be done in a few minutes. Samandriel, now that your father is home, why don't you go set the table?"

Samandriel took the hint, standing up and half-running for the kitchen. Castiel waited, staring at his socked feet, as his husband pattered around, loosening his tie and removing his suit jacket.

"A puzzle, is it?" Crowley's voice was low, dangerous, and Castiel could not control the shiver that ran down his spine. "Surely you have more useful things to do with the boy than play games, Castiel. Have you even started teaching him how to clean, like I told you to?"

"Yes," Castiel answered quietly, daring to glance up into his mate's cold, impassive face. "He cleaned the bathrooms all by himself today. And I taught him how to make the sauce for the roast. It's just that he's a child, and we had some time after the chores were finished, so I thought—"

"I didn't marry you for your thoughts, Castiel," Crowley replied coolly. "You're an Omega. You're not supposed to think. Neither is our son. I won't have you raising him the way you would an Alpha or a Beta. You keep this up, and I will send Samandriel off to a single sex boarding school to learn his place—is that clear?"

Castiel nodded, swallowing the lump in his throat. He had prayed, when his son was born, that he would turn out to be an Alpha or a Beta, and be spared the fate that had fallen upon Castiel himself. Luck had not been on his side; Samandriel was an intelligent, kindly child, but he was an Omega, and in Crowley's household, biology superseded all else. There was still plenty of time for him to have more children, to give his husband an Alpha or a Beta, and if his late heat this month was any indication, there was a good chance that this would happen sooner rather than later, but the sex of any future children would not spare Samandriel an upbringing as a proper house-spouse. There were no dreams of college or a career for Omegas under Crowley's roof.

"We will handle this properly later," Crowley said dismissively, turning on his heel to leave the room. Castiel released the breath that he had been unaware he was holding and wiped his sweaty palms on his dress pants. He took a moment to compose himself, and headed into the kitchen to put out the salad and check on the roast. Dinner would not serve itself, after all.

As always, dinner was a quiet affair in the MacLeod house. Crowley talked about his day in between bites, and Castiel and Samandriel listened silently, smiling and nodding in all the right places. After the meal, Crowley poured himself a glass of well-aged scotch, and Castiel helped walk Samandriel through doing the dishes. All too soon, the left-overs were stored in the fridge and the dishwasher was full and running, returning the dishes to their sparklingly clean state. "Bed," Castiel ordered softly, with a glance at the clock. It was not even eight, but Samandriel was used to going to bed early, and Castiel's tone broke no nonsense. His son did not question him, slipping upstairs as quietly as possible to brush his teeth and put himself to bed.

Castiel slunk into the living room, dropping submissively to his knees at Crowley's feet. "Please forgive me," he whispered, resting his head against the seat of the couch. The words slid easily from his tongue; it had not mattered what he was apologizing for in years, after all. He could get through the rest of the night on autopilot, unless something went terribly wrong.

"Very well, pet," Crowley said carelessly, setting his drink down on the coffee table. "Up, on the couch," he ordered. Castiel scrambled to obey, clasping his hands tightly between his knees and keeping his gaze on the floor. "You understand what you did wrong, and you have apologized. I do not see the need to punish you tonight."

"Thank you, Alpha," Castiel whispered, allowing Crowley to slip his hands around his waist. He shivered as the cloying scent of musk and scotch assaulted his nose, but allowed his mate to draw him in for a kiss.


	2. Defiance

Warning for domestic violence and verbal abuse. Everyone, please give Cas a hug.

* * *

"Rise and shine, bitch!"

Sam groaned, tempted to throw his phone across the room as his brother's much too chipper voice sounded in his ear. "Dean, what are you doing calling me this early?" he demanded groggily. Beside him, Kevin stirred, shifting slightly and pulling the covers tightly around his face. Sam laid a large hand on his mate's side, rubbing soothing fingers across his skin. Kevin stilled, and Sam could not help the slight smile that crossed his face. Stretching, he kicked his feet over his side of the bed, rolling his shoulders to loosen stiff limbs as he left the bedroom for the quiet living room, dimly lit by the half-risen sun.

"Got an unexpected day off. Gordon said he's going to be short on rent this month, wanted to take my shift,. Wanted to ask you and Kevin over to dinner tonight, if you're free."

"You called me at six in the morning for this?" Sam knew that Dean knew better than to take his annoyance seriously. His brother had always called him an overgrown puppy, and though Sam would never admit it, in some ways, it was true. He might bitch at Dean, but he could never seem to be truly angry with him.

"Well, yeah, it kind of determines what I'm doing with the rest of my day." Dean chuckled, and Sam was glad that his brother could not see the grudging grin that slid across his face. He had to keep up his put out act _some _of the time.

"Yeah, sure, I'll ask Kevin when he gets up, but I can't imagine he would say no." In fact, Sam knew that his mate would be delighted to have a ready-made excuse to drop by Dean's house. Two missed heats and a month of near-daily morning sickness could only mean one thing, and Sam and Kevin had long since decided that they wanted to announce the coming of their first child to their family and friends in person. "What time do you want us here?"

"Just drop on by sometime in the afternoon." Sam could swear that he could hear his brother's grin through the phone, and he felt a pang of guilt; Dean lived alone, and he had been remiss about visiting him. Not that his brother would ever complain about feeling lonely, not when he hardly seemed to register it as an emotion, but he always seemed inordinately delighted to see Sam and Kevin every time they came over. Sam made a mental note to get out to his brother's place more often; it wasn't exactly a long drive.

"Okay. If it's all right, I'm going back to bed, now," Sam said, shaking his head as his brother huffed indignantly.

"Yeah, all right. See you this afternoon, then, bitch!"

Sam smiled affectionately at the demeaning nickname. "Jerk," he responded, ending the call before his brother could get another word in. He yawned, stretching, unable to deny the butterflies that shot through his stomach. For all his talk about going back to bed, he doubted that he would be able to sleep now. Not when in only a few hours, he would be announcing his mate's pregnancy to his brother. Dean would be over the moon that he was the first to know.

"Sam?" Kevin poked his head out of the bedroom, his thick black hair rumpled and hanging in his face as he rubbed the sleep from his eyes. "What's going on?"

"Dean invited us to dinner tonight," Sam replied, grinning at the adorable picture his sleepy mate made. "That good with you? We can tell him about the upcoming addition to our family."

Kevin blinked tiredly, taking a few minutes to run Sam's words through his undoubtedly sleep-muddled brain. "Oh!" he exclaimed finally, his face lighting up. "Yeah, of course! Sounds awesome!"

Sam laughed, walking over to his mate and folding him into his arms, affectionately kissing the top of his head. "I don't know about you, but I don't think I'm going to be able to get back to sleep," he said, a hint of question in his voice.

Kevin hummed, rubbing his face against his mate's strong, broad chest. "I might have a few ideas on how to remedy that," he said, taking Sam's hand and pulling him into the bedroom.

0o0o0o0o0

Dean had just finished wiping down the table and had cracked open his first beer of the day when a knock sounded at his door. "It's open!" he called, brushing his hands on his jeans and making his way into the living room.

Sam stood in the doorway, his huge frame nearly hiding Kevin, who stood almost directly behind him. "Hey, little brother!" Dean greeted him, seizing his brother around the waist and dragging him into a tight bear hug. "It's been way too long. Hiya, squirt," he teased, reaching out to drag his brother's mate into the embrace, squeezing them both and letting go, stepping back to grin at the both of them. "You're way earlier than I expected. Dinner's not going to be ready for a few hours."

"Such a problem. We only came over for your food, you know," Sam replied sarcastically, rolling his eyes as he returned his brother's smile. Dean snorted, closing the door behind them.

"Fridge is free game if you want drinks or a snack. Basketball's on TV, but feel free to change the channel if you like. I only put it on for background noise." Dean laughed at the look on Kevin's face; the other Omega practically ran for the remote, flicking through the channels and settling on some scientific documentary that he'd likely been angling to watch today. Sam shook his head, amused, and ducked into the kitchen, returning with a beer in one hand and a water bottle in the other. He tossed the water to Kevin, who caught it without looking, already engrossed in the researchers on screen.

"So, Dean," Sam said when they had all settled on the couch, the TV at half volume in the background. Kevin glanced up sharply, turning the volume down almost to mute and swiveling to face his brother in law. "Before we get too wrapped up in things, there's something Kevin and I need to tell you."

"Shoot," Dean said, flashing a charming smile at the pair.

Kevin took an excited breath. "How do you feel about being an uncle?" he asked, his hands drifting unconsciously towards his stomach.

"Like I'm going to spoil the hell out of any kids you guys have," Dean answered easily, taking a long sip of his beer. "Why, you guys thinking about trying for a kid soon?"

He was greeted with an excited silence. Sam grinned, ducking his head almost shyly as Kevin reached for his hand. "Oh no way," Dean breathed, looking from Kevin to Sam and then back again. "You're pregnant?" he blurted out, his voice rising in excitement. "Holy shit! Since when?" he demanded breathlessly.

"Um, about two months," Kevin said shyly, running his thumb over Sam's palm. "We haven't told anyone else, but it seemed like it's all good to let you know."

Dean swallowed hard, absolutely speechless. The first to know about such a momentous event in his brother's life? Shaking his head, Dean took a moment to compose himself. "Right, well, as an uncle to be, I have a long list of demands, and you don't get to say no to any of them," he said, only half joking. "You call me when you find out if it's a boy or a girl. You call me when you figure out a name. You call me when you get the first ultrasound pictures…"

0o0o0o0o0

Castiel was hard at work scrubbing the kitchen floor when the house phone rang. Tiredly, he wiped his brow with his apron, before rising and making his way to the phone by the fifth ring. The caller ID read "Lawrence Elementary" and he felt a stab of worry. Why would Samandriel's school be calling him?

Castiel swallowed hard and picked up the phone. "MacLeod residence," he said, tapping his fingers nervously against his thigh.

"Mr. MacLeod?" Castiel grimaced at the static that buzzed over the voice on the other end.

"Speaking," he replied, glancing at the clock. Not even noon; it was still the middle of the school day. He hoped that Samandriel had not gotten sick. "How may I help you?"

"Mr. MacLeod, we are calling about your son Samandriel. He is with the principal right now, and we need to schedule a parent-teacher conference."

With the principal? "What happened?" Castiel asked, sinking to the floor before his knees could give out on him. This was not good. Crowley would be livid about having to take off work, and there was no way that he would allow Castiel to attend a parent-teacher conference on his own.

"Your son's teacher has brought him to the office with a complaint. It seems Samandriel has developed a habit of arguing with his teacher whenever he does not see the point to an assignment. Naturally, Mr. Fitzgerald is concerned that there might be something going on, either at home or in the classroom, that is encouraging Samandriel to act out. It's a fairly routine procedure; we just want to ensure that we are doing everything we can to make school a pleasant and fulfilling experience for all our students."

Castiel's blood ran cold. "There must be some mistake," he said finally, his voice shaking. It was impossible. Samandriel couldn't be acting out—he knew better. He knew that there would be severe consequences if Crowley found out! "My son is a good kid. He wouldn't argue with his teacher."

"I'm afraid that he is." The voice on the other end was all business, oblivious to the terror that shot through Castiel's heart. "We have already contacted your spouse about the matter, and he requested that we call you for your input."

Castiel fought back hysterical laughter. For his input? More likely Crowley wanted to strike fear into him, make him miserable and on edge until he got home and could properly punish his family. "Yes, well, if a conference is necessary, please schedule for your nearest convenience," he said, his mouth running on autopilot, his mind a thousand miles away. He could find a way to make this up to Crowley. He had to, because there was no way he could allow his child to be punished simply for questioning what he was told. Crowley would see it differently, but Castiel could distract him, take his mind off the issue. It would have to work.

Castiel was hardly aware of writing down the appointment time and bidding the person on the other end of the phone farewell. He hung up and drew his knees up to his chest, shaking. This couldn't be happening.

Castiel sat for hours, lost in his panic, until the rumbling of the school bus pulled him from his thoughts. Swallowing hard, he rose and made his way unsteadily to the door. It would not do for Samandriel to see him, panic-ridden, on the floor. He had to be a parent before all else.

"Samandriel, what were you thinking?" he demanded before his son even had time to take off his shoes. The six year old looked up at Castiel, his eyes wide, but his mouth set in a thin, stubborn line.

"The assignment was stupid," he said, bending down to untie his sneakers. "Mr. Fitzgerald wanted us to add carrots. Carrots, Papa, not numbers. It was stupid, and I told him so. Why would we add carrots anyways?"

"That's not—" Castiel sucked in a breath, steadying himself. "The school called your father," he said, his voice hard. "You know that he prizes obedience over everything else. Do you have any idea how furious he's going to be?"

"But it was _stupid, _Papa," Samandriel protested, clutching the strap of his backpack in a small fist.

"It doesn't matter if it was stupid!" Castiel cried, steading himself against the back of an armchair. "You don't argue with your teachers! Ever!"

Samandriel glared at him with all the self-righteous fury of his six years. Castiel's insides clenched, because really, his son had not done anything wrong, and yet his actions would have severe consequences. "Go to your room," he ordered finally. "Do your homework. I don't care if your homework is adding carrots, or something else you think is stupid, you do your work and you don't complain about it. Do I make myself clear?"

Samandriel released a long, exasperated sigh, glowering as he stomped off towards the stairs. Castiel took a shaky breath, rubbing his hands against his face to steady himself. Oh, Crowley was going to be livid. His knees threatened to give out, but he had dinner to make and a house to clean, and slacking off on his chores would only provoke his husband further.

It was only a few hours before Crowley returned, earlier than usual, slamming the door behind him. Castiel jerked reflexively, nearly burning himself as he lurched dangerously close to the stove. He shook his head, turning the heat down to a low simmer, and turned, forcing himself to leave the kitchen and face the music out in the living room.

"I take it you got the call," Crowley said without preamble, glaring at his mate.

"I did," Castiel replied, his voice wavering. "I sent him to his room to work on his homework. It won't happen again, I promise."

"No, it won't," Crowley agreed amicably. "I am withdrawing him from public school. Clearly, you've been a bad influence, Castiel. Not half as obedient as an Omega should be, and he had to learn this behavior somewhere."

Castiel gasped, struggling to suck air into his lungs. "Crowley—"

"Don't," his mate snapped, glaring at him. "I've already made the arrangements. From now on, he will be enrolled in Angeli's School for Omegas. They're sending a car for him tonight."

"Please," Castiel begged, sinking to his knees, desperate to placate his husband. "It was his first time making this kind of mistake. Please, just let me—"

"See, and this is exactly what I'm talking about!" Crowley barked, slamming his fist against the wall. Castiel jumped, his heart hammering as he stared up at the enraged man before him. "An Omega does not question his mate, Castiel. I don't know where you learned this behavior, but it ends now. When I tell you our son is a disgrace and I am shipping him off to boarding school to rectify his behavior, you accept it without complaint, do you understand?"

Castiel shook his head wildly, aware that he was on thin ice, but unable to bring himself to care. "Crowley, please, let me—"

Crowley seized him by the shirt lapels and hauled him to his feet. "What did I just say?" he growled, shaking Castiel hard. "Well?"

Castiel shook his head. With an angry snarl, Crowley backhanded him, snapping his head back with the force of the blow. "You're a disgrace," his mate snapped, glaring at him with disgust. "I ought to throw you out right now. See how an Omega with barely a high school diploma gets by when he has to take care of himself. You wouldn't last a week before you came crawling back to me!"

"Do it." The words were out of Castiel's mouth before he could stop them. "Do it! Because—because if you send Samandriel away, I'm leaving you," he babbled, ignoring the voice in his head that screamed at him to shut up before he made the situation worse.

Crowley stared at him in disbelief. "You wouldn't dare," he said finally, dangerously. "You think I don't know that you missed your heat this month? You think you can raise a child on the streets?"

"At least on the streets, if it's an Omega, my child won't grow up thinking that they're less than everyone else just because of who they are!" Castiel shouted, wrenching out of Crowley's grasp.

"You're right! He won't grow up at all! He'll die before you've even weaned him, you useless bitch!" Crowley grabbed at Castiel, but he dodged, backing away warily. Crowley took a step towards him; Castiel turned and bolted for the stairs.

He had to get to Samandriel, the need to grab his son and leave singing through his veins. Primal instinct propelled him, and Castiel tore up the stairs, sprinting down the hall to Samandriel's room at the end.

A sudden blow threw Castiel into the wall. He yelled in surprise and pain as the impact jolted through his body, stunning him. Crowley's hard, angry hand closed around his neck; almost effortlessly, he picked Castiel up and threw him in the guest room, shutting the door. Castiel heard the click of a lock, and grabbed desperately at the handle. The door would not budge.

"I will deal with you when my son is safely off to his new school, where you can no longer influence him." Crowley's voice was muffled through the thick wooden door, but no less menacing for the barrier.

"Let me out!" Castiel screamed, banging his fists uselessly against dark mahogany. "Please! Alpha, _please, _at least let me say goodbye to him!"

"You lost that right when you threatened to leave," Crowley replied, his voice distant. He was moving down the hall, doubtless going to Samandriel's room, to take Castiel's son and send him away to some wretched school of brainwashing. Castiel would only see him on holidays, and even then, he would be a shell of himself, warped and broken by the oppressive values of single sex schools.

Castiel wailed, sinking to the ground and curling in on himself. He wept for his son, born into a life of oppression, and for himself, for the dreams he lost when he made the rash decision to run off with Crowley. If he had not been so stubborn, so desperate to get away from his family, maybe he would be happy and free right now. Instead, he was little more than a slave to Crowley's beliefs and appetites, and the one person who made his life worth living, his son, was being taken from him.

He had to leave. Whatever the cost, he had to get away from Crowley. Maybe his husband was right; maybe he would end up alone and helpless on the streets, dying early from exposure and neglect, unable to fend for himself. At least then he would die free.


End file.
